Many food products contain flavoring agents obtained by the hydrolysis of proteinaceous material. Conventionally hydrolysis is accomplished by using strong acid, followed by neutralization. Acid-hydrolysis requires the use of aggressive chemicals and can be energy consuming. Furthermore it often leads to the severe degradation of the amino acids obtained during hydrolysis.
Protein degrading enzymes can also be used to protein hydrolysis because they are less polluting than the strong, aggressive chemicals used in acid hydrolysis and are also capable of working under mild conditions that prevent the racemization of amino acids. Typically the aim of enzymatic hydrolysis of proteinaceous material is to obtain a high degree of hydrolysis, usually by using a cocktail of nonspecific-acting proteolytic enzymes, both endo-peptidases and exo-peptidases. Specific acting proteolytic enzymes are not used for this purpose because such enzymes provide an inadequate degree of hydrolysis. Conversely, where the aim is to produce specific amino acids or peptides from a complex protein without destroying the protein's physical properties (such as its elasticity, foaming properties or texture properties) specific acting enzymes are preferred.
Many microorganisms are able to produce endo-proteases and exo-proteases. In the food industry, Aspergilli have been widely used for a long time and are, therefore, in conformity with safety regulations in many countries all over the world. Among the Aspergilli, Aspergillus niger is the most widely used species in the food industry. Aspergillus niger has been used as a source of proteolytic enzymes in the past. For example, WO 96/38549 describes the production of a culture filtrate from an Aspergillus niger strain, the filtrate exhibiting aminopeptidase activity, and substantially lacking endo-proteolytic activity. However, the aminopeptidase activity in the crude filtrate was relatively low, and the source of the enzymatic activity was never isolated or specifically identified.